1. Field of the Invention
The present invention relates to a circuit for outputting only a normal signal pulse by removing a noise signal.
2. Description of the Related Arts
As illustrated in FIG. 2, in a conventional noise removing circuit for removing noise from a digital signal, an input signal is branched into two signals: a signal to be inputted to a gate circuit (corresponding to an AND gate circuit 16 of FIG. 2) and a signal to be inputted to a delay circuit 15. The delay circuit 15 delays the input signal to output the delayed signal, and the delayed signal is inputted to the gate circuit. The gate circuit performs calculation to obtain a logical multiplication or a logical addition (a logical multiplication is obtained in FIG. 2) of the two inputs, and outputs the result.
The delay circuit 15 delays the input signal by an amount larger than the width of a noise pulse, and the delayed signal is inputted to the AND gate circuit 16. The AND gate circuit 16 obtains a logical multiplication of the input signal and the input signal delayed by the delay circuit to thereby remove a noise pulse. The AND gate circuit 16 then makes the trailing edges of signal components of the input signals to be in phase with each other to generate a final output signal (see, for example, JP 06-132791 A).
However, in application of such the conventional noise removing circuit there is a problem in that, when a noise pulse inputted has a width that is equal to or larger than a delay time of the delay circuit, a noise pulse having such a width can not be removed and allowed to be passed along with a normal signal pulse.
Further, the pulse width of an output signal outputted from such the conventional noise removing circuit has a pulse width corresponding to a pulse width obtained by eliminating the delay time from an output signal, which leads to another problem in that it is difficult to make the signal in phase with a clock signal in a subsequent stage.